Antimicrobial Activities of Streptomyces Species Isolated from Various Soil Samples in Federal University of Technology, Akure Environment

IOSR Journal of Pharmacy and Biological Sciences (IOSR-JPBS) e-ISSN: 2278-3008, p-ISSN:2319-7676. Volume 10, Issue 4 Ver. III (Jul - Aug. 2015), PP 22-30 www.iosrjournals.org Antimicrobial Activities of Streptomyces Species Isolated From Various Soil Samples in Federal University of Technology, Akure Environment Ogundare, A. O., Ekundayo, F. O.and Banji- Onisile, F. Department of Microbiology, Federal University of Technology, PMB 704, Akure, Ondo State Nigeria Abstract: Five (5) different species of Streptomyces were isolated from different soil samples obtained from the Federal University of Technology, Akure, Nigeria and were tested for antagonistic activity against 5 pathogenic bacteria and fungi respectively. During the primary antimicrobial screening, 12% of the strain showed inhibitory potentials against the test microorganisms. The active metabolite was extracted using chloroform. Purification of the extract was performed using column chromatographic technique. Infra-Red spectroscopy carried out on the active fraction revealed four important functional groups which were hydroxyl, carbon- hydrogen, carbonyl and aromatic groups. The nucleotide sequence of the 16S RNA showed 83% identity with Streptomyces albus. From the taxonomic feature, the Streptomyces isolate DSM 40313 matched with S. albus in the morphological, physiological and biochemical characters. Thus, it was assigned the name Streptomyces albusDSM 40313. Keywords:Streptomyces, test microorganisms, soil samples, antagonistic activity. I. Introduction Streptomyces are gram positive, spore-forming bacteria found in soil. They are characterized by their tough, leathery, frequently pigmented colonies and their filamentous growth (Euzéby, 2008). They have genomes with high guanine and cytosine content (Madigan and Martinko 2005). Streptomyces is the largest genus of Actinobacteria and the type genus of the family Streptomycetaceae (Kämpfer, 2006). The production of a number of toxic natural products by Streptomyces isolates was long thought to be a competitive mechanism for the bacteria. Species of this genus are unusually prolific in the production of antibiotics and other types of compounds that are deleterious to competing microorganisms(Laskariset al., 2010).They also have unusually large genome sizes, presumably because of their production of these secondary compounds. Streptomyces griseushas been shown antibioticssuch as streptomycin (Laskariset al. 2010).The resistance of numerous pathogenic bacteria and fungi to commonly used antibiotics require an urgent focus of research and since Streptomyces is the most abundant actinomycete group in soil (Otoguroet al., 2001; Ramakrishnanet al., 2009), Extensive screening of this genus Streptomyces will therefore lead to the discovery of many novel strains that produce useful secondary metabolites necessary to combat these resistant pathogens. This study was therefore investigated to isolate Streptomyces from some soil samples from FUTA environment II. Materials and Methods Sample collection and isolation Soil samples were collected from household waste dumping site, ploughed soil, plantain cultivated soil, vegetative (weed) soil, loamy, sandy and clayey soils. The samples were transferred to the laboratory for further analysis.Plates containing starch casein medium were used for isolation of the Streptomyces. Different species of Streptomyces were isolated using the serial soil dilution technique as described by Olutiolaet al. (2000). Plates were incubated for 5 days at 28oC. Streptomyces colonies were picked from each plate and were streaked onto fresh plates until pure cultures were obtained. The isolates were identified using Gram-staining, catalase production, citrate utilization, starch hydrolysis, and fermentation of sugars according to the protocols of Olutiolaet al. (2000) and Cheesbrough (2006). Screening of Streptomyces for antimicrobial metabolite production Fresh culture of Streptomyces was inoculated in starch casein broth and incubated at 280C for 7 days in water bath with shaking. Growth of the organism in the flask was confirmed by turbidity in the broth. The broth culture was centrifuged at 5000 rpm for 20 minutes and the supernatant was filtered through No 1 Whatman filter paper. The culture filtrate of the Streptomyces species was used for the determination of antimicrobial activity against the test organisms (Singh and Agrawal 2003). Molten agar was aseptically dispensed into Petri dishes containing 1ml of each test organism and was allowed to gel. The seeded plates were allowed to set and wells at equidistant from each other were made in the agar plates with the aid of a cork borer (diameter 10 mm). DOI: 10.9790/3008-10432223 www.iosrjournals.org 22 | Page AntimicrobialActivities of StreptomycesSpecies Isolated From Various Soil Samples… Each well was then filled with 0.1ml of the culture filtrate. The plates were allowed to stand for one hour to allow diffusion of the metabolite in the filtrate, then incubated at 37°C for 24 h and observed for zones of inhibition. Three replicates of the experiment were performed and the diameters of the inhibition zones were measured and recorded. Extraction and bioassay of antimicrobial metabolite Extraction of crude metabolite Antimicrobial compound was recovered from the culture filtrate of S. albus (Streptomyces whose filtrate gave the highest zone of inhibition value) by solvent extraction with chloroform. Chloroform was added to the filtrate in the ratio 1:1 (v/v) and shaken vigorously; the organic phase containing the metabolite was separated from the aqueous phase. The extract obtained was evaporated to dryness using rotary evaporator and the crude extract was then used for bio assay (Owolabi and Olarinoye, 2008). Antimicrobial assay of the crude metabolite Antimicrobial activity of the crude metabolite was determined by agar well diffusion method as described by Olutiolaet al. (2000). The test organisms were standardized to 0.5 McFarland standards as described by Oyelekeet al. (2008). Sterile Petri dishes were seeded aseptically with 1ml each of the standardized broth cultures and 20ml of sterilized Mueller- Hinton agar was poured aseptically on the seeded plates. The plates were swirled carefully for even distribution and allowed to gel. With the aid of sterile cork borer, wells were created on the solidified agar medium. Exactly 0.5mL of 50mg/mL of the metabolite was then introduced into the wells and approximately labeled. The plates were incubated for 24 h at 37oC in case of bacterial species and 28oC for three days in case of fungal species. The plates were observed for zones of inhibition (Atta et al., 2009). Thin Layer Chromatography (TLC) The crude extract was subjected to TLC analysis on 2.6 × 8 cm silica gel plate. This was spotted onto a TLC plate 2 cm above the base. After thorough drying, the plate was placed in a solvent system (chloroform: methanol in the ratio 2:1) in a chromatography tank to develop. The plates were removed when the solvent front approached the top of the plates and air-dried. Spots on the plates were visualized in an iodine chamber. The distances travelled by the constituents were measured and used to determine their Rf values(Atta, 2009) Purification by Column chromatography The purification of the antimicrobial compound was carried out using silica gel column chromatography as described by Atta (2009) and Ushaet al. (2010). Chloroform and methanol in the ratio 2:1 v/v was used as eluting solvent. The column was packed with silica gel (60-120 mesh). The sample to be separated was then added on the top of the packed column and eluted with the solvent at the flow rate of a drop per 3 sec. A collecting conical flask was placed at the bottom of the column to collect the eluted fractions. The collected elute was distilled, leaving the purified fractions. The fractions obtained were spotted unto TLC plates. Fractions with the same retention factor (Rf) were pooled together. Antimicrobial Assay of column fractions of crude metabolite Antimicrobial activity of the column fraction was determined by paper disc diffusion method (Aida et al., 2001). Sterile Petri dishes were seeded aseptically with 0.1ml of the standardized test organisms while about 20ml of sterile Mueller Hinton agar was poured aseptically on the seeded plates. Sterile Whatman filter paper discs (6.00mm in diameter) were impregnated with 30mg/ml of the purified fraction reconstituted with 30% dimethyl sulphonamide (DMSO). The impregnated paper discs were allowed to dry and applied with the aid of sterile forceps on the seeded plates. Filter paper disc dipped into DMSO and allowed to dry served as control. The plates were incubated at 37oC for 24 h. Antimicrobial activities were determined by the measurement of zone of inhibition around each paper disc. Determination of Minimum Inhibitory Concentration (MIC) of the metabolite. The determination of Minimum Inhibitory Concentration (MIC) was carried out using agar well diffusion method as described by Magaldiet al. (2001). Varying concentrations of the metabolite (30mg/mL, 15mg/mL, 7.5mg/mL, 3.75mg/mL and 1.8mg/mL) were reconstituted in 30% DMSO. Sterile Petri dishes were seeded aseptically with 0.1mL of the standardized test organisms while about 20mL of sterile Mueller Hinton agar was poured aseptically on the seeded plates. The plates were swirled carefully for even distribution and allowed to gel. Five wells were created on the agar and the metabolite was introduced at different concentrations into the

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